Although generally applicable to windows for any kind of aircraft, the present disclosure and the problem on which it is based will be explained in greater detail with reference to commercial passenger aircraft.
The windows of modern passenger airplanes typically feature a fail-safe design based on a double-pane window concept. Here, a pressurized outer pane and a none-pressurized inner pane are spaced apart from one another with a window interspace in between filled with air. The panes themselves are often formed from a transparent thermoplastic material like polymethyl methacrylate (PMMA), also known as acrylic or acrylic glass, which is relatively lightweight and shatter-resistant compared to plain glass. Both panes are fixed and sealed to a window frame, which amongst others may include a spacer or similar that sets the window interspace to a desired depth. Usually, both panes are assembled within one common window seal as a joint window set, which in turn is fixed to the window-frame from the inside of the aircraft by a so-called retainer that covers the window seal together with the outer rims of the window panes and the window frame. Such a double pane design, as disclosed for example in documents EP 0936138 B1, EP 0846615 B1 and EP 0846616 B1, has the important advantage that the panes form a thin air gap, which enables fogging-free behavior of the window assembly.